The objective of this project is to develop novel inhibitors of herpes simplex virus (HSV) replication. HSV is the etiologic agent of a number of clinically significant human diseases. In phase I research, antisense oligonucleotides complementary to HSV genes known to be essential for viral replication were designed, synthesized and screened for antiviral activity in cell culture based assays. Focusing on three of the most active compounds, we propose in phase II development to verify activity in alternative cell culture assays and against several isolates of both HSV serotypes. Cellular toxicity will be carefully evaluated and antiviral activity in cell culture will be optimized for each oligonucleotide with respect to length and sequence composition. The specificity and mechanism of anti-sense mediated inhibition of HSV gene expression will also be analyzed. Antiviral activity of antisense oligonucleotides with acceptable in vitro profiles will then be evaluated in relevant animal models of HSV induced disease. This research will provide the basis for Phase III preclinical and clinical development of antisense oligonucleotides which exhibit pharmacological and toxicological profiles suitable for use as human pharmaceutical products.